Satellite Orbit and Ephemeris Determination using Inter Satellite Links

Inter Satellite LinksOrbit Computation( LatS + LatS1 ⋅ ( t − t )) ⋅sin(θ)LatS(t) = Harmonic sine correction0term of latitudewith θ = ω E⋅ UTCEq. 4.4-30being the hour angle. Both, latitude and longitude harmonic corrections, account for periodicerrors with increasing amplitude (see section 4.3-Force Model Errors).The resulting longitude and latitude of the space craft is obtained by adding all correction ofsecular and harmonic terms.Lon = Lon + Lon + LonEq. 4.4-31Lat = LatCM+ LatSCSUnfortunately, this ephemeris format is not intended to account for radial perturbations(However it could easily be modified to do so!). For communication purposes like televisionbroadcast, only elevation and azimuth of the satellite are necessary to align the dish antenna.But for navigation, the radial component is the most important, due to its large impact on theranging error.Driven by the requirement for accurate pointing instead of accurate ranging, the period ofvalidity is one week. Nevertheless, the transformation to Cartesian co-ordinates is givenbelow.x = R ⋅ cos Lon ⋅ cos LatEq. 4.4-32y = Rz = RGEOGEOGEO⋅ sin Lon ⋅ cos Lat⋅ sin Latwith R GEO = 42164537 mR. Wolf Page 69